Global structure of zonal flow and electromagnetic ion temperature gradient driven turbulence in tokamak plasmas

Miyato, Naoaki; Kishimoto, Yasuaki; Li, J.

Global characteristics of the coupled system of zonal flows and electromagnetic ion temperature gradient driven turbulence in tokamak plasmas are investigated using a global electromagnetic Landau fluid code. Zonal flow behavior changes with the safety factor . In a low region stationary zonal flows are excited and suppress the turbulence effectively. Coupling between zonal flows and poloidally asymmetric pressure perturbations due to a geodesic curvature makes the zonal flows oscillatory in a high region. Energy transfer from the oscillatory zonal flows to the turbulence via the poloidally asymmetric pressure perturbations is identified. Therefore in the high region where the zonal flows are oscillatory, the zonal flows cannot quench the turbulence and turbulent transport is not suppressed completely. As for the zonal flow behavior, it is favorable for confinement improvement to make the low region where the stationary zonal flows are dominant in tokamak plasmas.